Intertherm M3RL080A

[jsta]

Inducer Blower limits out the 145 degree swich. Push the switch button and it resets and works for a while. The red light is flashing when it limits out.

I have tried the following:

Replace the 145 degree limit switch on the inducer.
Left the cover off
Vac'd out the exhaust and intake vents. Small particles as described below, but small amount.
Removed the inducer, there was a hardened gasket or maybe glue substance formed to the bottom of the inducer intake that was blocking it about 15-20%, this didn't fix it.

One thing that is unusual is that there is NO water being taken out of the exhaust? This heater vent goes up to the ceiling and then horizontal to above the garage, and I didn't notice any blockage.

I have this same heater upstairs and it vents straight up and pulls about a gallon every 48 hours.

My next thought is to potentially replace the inducer motor.

Ideas??

[Rod]

That hardened gasket behind the inducer is a resrictor/orifice. It is about the size of a silver dollar and should have a hole in the center about the size of a quarter. You described it as melted?
Nordyne is having some problems with these. I believe when these go bad too much air increases the flame and trips the switch. Hopefully one of the HVAC experts will jump in with some additional input.

Rod

[jsta]

I checked my upstairs inducer for the gasket and that one is basically gone. The gasket appears to just be a circle to prevent outside air getting into the inducer. Unless there is supposed to be extra gasket to make the opening smaller I don't think this is the issue?? What if outside air was allowed to get in. maybe that would be enough to keep it cool???

[Rod]

Let me clarify. The inducer orifice is a plastic restricter plate not a gasket. It sets into the bell housing and regulates how much air is mixed with the gas. This is the part that Miller has been having trouble with, and when they go they sometimes completely melt away. The Miller part # is 155315R. If this part is intact than you need to call a quaified Miller service tech. If you are not sure what part I am describing let me know and I'll try to post a picture.

Rod

[jsta]

Rod:

Hey I think that has to be it. Only thing left of that part is pieces, it is toast. I had it written down to ask the dealer if that wasn't the part number as I didn't have a picture but that is the only part number that makes any sense. I will replace them both. US was running at 158 and DS was running at 163 so the US is running close as well.

Thx for the help. Hopefully you wont see me on here in the near future

[Robert]

Hi,

For a Vent Safety Limit Switch tripping, check the following as well :

Blower speed
External Static Pressure
Firing rate
Dirty or clogged filter
Dirty secondary heat exchanger
Short cycling of blower



Thanks,
Robert